When I ran a railway station, we had a car on our car park for several days over its allotted time. We didn't charge for the excess parking because the owner had used one of our trains but then dropped dead when he got off at Liverpool Street!
If you can think of something equally dramatic you might get off ;-)
Incidentally, be wary of trying to state that there was a valid ticket (or disabled pass) displayed. Most parking officials now carry digital cameras and photograph all vehicles contravening the regulations, so that such claims can be disproved.
Chris